Translation: "Let me out, oh God please, please let me out, I promise to be good...."
Just kidding. It's a "do not enter" sign. Intentional or not, putting it BEHIND the fence was a nice touch. Cute portrayals of helmeted workers are a common sight on signs placed around construction sites in Japan. Why pay a guy to stand around when you can have a "working character" do it with even better effect?